In recent years, e.g., a liquid crystal display device has been widely used for a liquid crystal television, a monitor, a portable telephone, etc. as a flat panel display having features such as a smaller thickness and a lighter weight compared to a conventional Braun tube. Such a liquid crystal display device includes an illuminating device (backlight) and a liquid crystal panel. The illuminating device emits light and the liquid crystal panel displays a desired image by serving as a shutter with respect to light from a light source provided in the illuminating device.
The above illuminating device has been provided as an edge-light type or a direct type in which a linear light source composed of a cold-cathode fluorescent tube or a hot-cathode fluorescent tube is located on the side or underside of the liquid crystal panel. However, the cold-cathode fluorescent tube etc. contain mercury and are not easily recyclable when they are discarded. Therefore, an illuminating device using a mercury-free light emitting diode (LED) as a light source has been developed and put into practical use.
Specifically, a conventional illuminating device, as described in, e.g., Patent Document 1, includes a light emitting diode and a light guide plate that receives light from the light emitting diode and emits planar illumination light to a liquid crystal panel. In this conventional illuminating device, the light emitting diode is mounted on a mounting board, and the mounting board has a protrusion below the light emitting diode. Moreover, a mounting groove is formed in the bottom face of a frame on which the light guide plate is mounted. The protrusion is fitted into the mounting groove, so that the light from the light emitting diode can efficiently enter the light guide plate.
In order to meet the requirements such as large screen and high brightness for the liquid crystal display device, the illuminating device needs to include a plurality of light emitting diodes as light sources. Therefore, in a conventional illuminating device, as described in, e.g., Patent Document 2, a plurality of light emitting diodes are arranged in a line on a mounting board, and a plurality of wires connected to the light emitting diodes are also provided on the mounting board and located below the light emitting diodes. Moreover, in this conventional illuminating device, a frame has a bottom face on which a light guide plate is mounted and a side face to which the mounting board is attached, and a groove is formed between the bottom face and the side face of the frame. Thus, the end portion of the mounting board in which the wires are provided can be placed in the groove even if the number of light emitting diodes to be mounted is increased.